The invention relates to a marine drive having two counter-rotating surfacing operating propellers.
The invention arose during development efforts directed toward a marine drive enabling increase top end boat speed. Surfacing drives for eliminating torpedo drag are known in the art, for example U.S. Pat. No. 4,871,334, column 3, lines 35+.
In one aspect of the present invention, the drive housing is provided with a skeg extending downwardly from the torpedo portion and having a forward leading edge with upper and lower ends, and an aft trailing edge with upper and lower ends, wherein the upper end of the leading edge is spaced forwardly of the lower end of the trailing edge by a horizontal distance greater than the horizontal length of the torpedo portion, for full rudder control.
In another aspect, the skeg has a first zone with outer surface profiles along horizontal cross-sections, the outer surface profiles being continuous along the first zone and defining continuous skeg sidewalls therealong. The skeg has a second zone above the first zone and with outer surface profiles along horizontal cross-sections, the outer surface profiles along the second zone being discontinuous and defining skeg sidewalls with an opening therein. The horizontal cross-sections along the second zone having the discontinuous gaps therein define a cored passage within the skeg communicating with the openings in the sidewalls. The openings in the sidewalls provide water inlets, and the cored passage provides a water passage extending upwardly in the housing. The torpedo portion has a third zone above the second zone and with outer surface profiles along horizontal cross-sections, the outer surface profiles along the third zone being continuous and defining continuous skeg sidewalls along the third zone. The horizontal cross-sections along the third zone have gaps therein defining the continuation of the cored passage upwardly within the skeg and communicating with the torpedo portion.
In another aspect, the skeg has a forward leading edge, and right and left sidewalls extending from the leading edge rearwardly to respective right and left sharp trailing edges providing a sharp break-off releasing water flowing therepast and minimizing water curving back therearound including at the surface below the propeller hubs.